update/delete inside for loop in SP

assuming that I have 'My_table' with metadata:
'pk_record integer
value1 integer
indexed_value1 integer'

and I make in SP the following loop:

for select pk_record, value1, indexed_value1 where indexed_value1>50
into : pk_record, :value1, :indexed_value1
do begin
update my_table
...???
where pk_record=: pk_record;
end


So, how far can I go? Can I update indexed_value1 field, or even pk_record field? Or can I safely update only value1 field. Does FB firstly make some set of selected rows and in for I can do anything, or there exists some things to which I have to pay special care?

Besides - do any incompatibilities exist for this issue between IB and FB?

Thanks in advance.

If you want to update only one, current record, there should not be any problems. You can use cursor for it:


CREATE PROCEDURE ... AS
BEGIN ...
FOR SELECT x,y,z
FROM tab
INTO :a, :b, :c
AS CURSOR cur
DO BEGIN
...
UPDATE tab SET ... WHERE CURRENT OF cur;
...
END
END